1. Field of the Invention
The present invention relates to lubrication devices for tractor-trailers, and particularly to a pneumatic greasing system for the fifth wheel of a semitrailer rig.
2. Description of the Related Art
A large quantity of manufactured goods and other cargo are transported by means of a tractor truck hauling a semitrailer in which part of the weight of the trailer is borne by the tractor. The semitrailer is usually coupled to the tractor by a device called a fifth wheel, comprising a generally round base plate pivotally mounted on a saddle bracket on the tractor chassis above the rear axles, and an upper plate on the bottom surface of the front part of the semitrailer. A kingpin depends from the upper plate which is locked into a slot or opening in the base plate so that the upper plate and the base plate are bearing surfaces on which the semitrailer is supported.
The upper plate rotates in contact with the surface of the base plate, the kingpin acting as the pivot, as the rig negotiates curves and turns. While the kingpin generally prevents any large longitudinal movements of the semitrailer with respect to the tractor, nevertheless, the bearing surfaces of the upper plate and the base plate are subjected to shearing forces from longitudinal movement of the semitrailer towards and away from the tractor, particularly as the rig goes up and down hills and the loads shift.
It is therefore of great importance to maintain lubrication between the bearing surfaces of the fifth wheel. Without lubrication the bearing plates are subjected to a tremendous amount of wear through friction and may seize, preventing rotational movement of the semitrailer. At best, handling of the truck becomes very difficult, and at worst the fifth wheel may seize at a critical moment, causing the vehicle to overturn.
The most commonly used method of lubrication is manual. The semitrailer is unhooked from the tractor and the driver applies grease to the base plate of the fifth wheel with a manual grease gun, or vehicle service personal will clean the old grease from the bearing surfaces and apply a new layer of grease with a pneumatically powered grease gun. Consequently, lubrication of the fifth wheel depends on conscientious adherence to a regular program of lubrication by the owner or operator of the tractor trailer. Unfortunately, regular lubrication maintenance schedules are often not adhered to due to the pressure of time constraints in a busy delivery schedule, or due to the inconvenience and mess associated with the process.
It is therefore desirable to have a process for lubricating the fifth wheel of a tractor and semitrailer which is quick, easy to perform, and which avoids the inconveniences associated with manually greasing the wheel. A variety of devices and processes have been proposed for improving the lubrication of the fifth wheel.
U.S. Pat. No. 3,622,173, issued Nov. 23, 1971 to D.W. Hodgson, describes a pair of fifth wheel plates having mating ridges and grooves with radial spaces extending through the ridges and grooves to better retain lubrication injected from outside the plates. U.S. Pat. No. 3,743,054, issued Jul. 3, 1973 to E.C. Jones, Jr., shows a fifth wheel having an upper plate welded to the trailer and a lower plate welded to the tractor. The trailer has a false bottom. A grease tube extends from a grease gun mounted on the outside of the trailer through the side of the trailer into the false bottom, the grease tube having openings which register with holes in the upper plate.
U.S. Pat. No. 4,541,651, issued Sep. 17, 1985 to R.E. Koster, teaches a liquid lubricant flowing from a reservoir outside the trailer by gravity to another reservoir above the upper plate. The second reservoir has a ball spring valve which releases lubricant between the plates. U.S. Pat. No. 4,805,926, issued Feb. 21, 1989 to G. Mamery, describes a self-lubricating plastic plate between the upper and lower plates of the fifth wheel.
U.S. Pat. No. 4,913,263, issued Apr. 3, 1990 to D. D. Spiers, teaches grease for the fifth wheel contained in plastic envelopes which are placed between the plates of the fifth wheel. The weight of the trailer crushes the envelopes to release the grease, the plastic disintegrating with rotation of the plates. U.S. Pat. No. 5,165,714, issued Nov. 24, 1992 to J. W. Kaim, shows a wear liner between the upper and lower plates of the fifth wheel for lubrication.
U.S. Pat. No. 5,522,613, issued Jun. 4, 1996 to J. P. Heeb, shows a plurality of lubricating pads secured to the lower plate of the fifth wheel, the pads having a steel underlayer with studs extending through orifices in the plate secured by nuts on the opposite side of the plate. The pads are made of a lubricating material, either nylon with embedded glass fibers, or polytetraf luoroethylene in a sintered matrix. German Patent No. 2,535,151, published Feb. 10, 1977, shows a saddle coupling with lubricated contact surfaces having several large grooves and numerous finer grooves over the surface of the coupler body for better distribution of grease injected into the large grooves through grease nipples inserted in holes in the side of the bearing plate.
Soviet Patent No. 698,831, published Nov. 25, 1979, teaches an intermediate plate with teeth which engage pawls, one pawl on the tractor and one pawl on the trailer. The plates ratchets when the vehicle turns in one direction but not in the other. The plate has radial channels fed from a lubricant reservoir. German Patent No. 3,118,633, published Nov. 25, 1982, shows a saddle coupler having Z-shaped grooves equipped with grease nozzles for circulating lubricant. The wheel also has outlet grooves to ensure a constant flow of grease.
European Patent No. 130,402, published Jan. 9, 1985, describes a coupler plate having a number of internal passageways for circulating lubricant, the passageways being formed by placing pipes in the mold when the coupler plate is formed. French Patent No. 2,596,497, published Oct. 2, 1987, teaches a pneumatic grease pump for a fifth wheel operated by compressed air from the air brake system, the grease being pumped into a network of grooves milled into either the saddle plate on the tractor or the yoke plate on the semitrailer. The grease pump is activated by a "detector" which detects a condition indicating the vehicle is being started. The grease pump provides grease for a predetermined time interval.
None of the above patents is seen to describe a grease pump powered by an independent supply of compressed air. None of the above patents is seen to describe a grease pan for a fifth wheel having a plurality of compartments on the bottom surface of the lower plate of the fifth wheel with a plurality of orifices communicating between the grease pan and the wheel for the delivery of grease. None of the above patents is seen to describe a pneumatically controlled system operated under electrical control by the operator of the rig, for a duration determined by the operator of the rig.
None of the above inventions and patents, taken either singularly or in combination, is seen to describe the instant invention as claimed. Thus a pneumatic greasing system for a fifth wheel solving the aforementioned problems is desired.